Detecting doublet bands in Western for eGFP control - (Sep/07/2012 )

hi guys

i seem to be detecting double bands in my westerns for my eGFP control. the bands are really close to each other and they apppear only in eGFP transfected cells.

from my sequence analysis, I dont see any mutations/alternative stop codons

can anyone tell me wat the heck is going on or wat i can do

(used both abcam 290 and living color mouse monoclonal anti-GFP)

Possibility of an alternative start codon or some codon slippage?